linux-kernel - Re: [PATCH v2] usb: core: Warn if an URB's transfer

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Date:   Tue, 25 Apr 2017 16:27:30 +0300
From:   Felipe Balbi <felipe.balbi@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Maksim Salau <maksim.salau@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        linux-kernel@...r.kernel.org, arnd@...db.de,
        Alan Stern <stern@...land.harvard.edu>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Peter Chen <peter.chen@....com>, Roger Quadros <rogerq@...com>,
        Baoyou Xie <baoyou.xie@...aro.org>,
        Sekhar Nori <nsekhar@...com>,
        Chris Bainbridge <chris.bainbridge@...il.com>,
        Wolfram Sang <wsa-dev@...g-engineering.com>,
        "open list\:USB SUBSYSTEM" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v2] usb: core: Warn if an URB's transfer_buffer is on stack


Hi,

Greg Kroah-Hartman <gregkh@...uxfoundation.org> writes:
> On Tue, Apr 25, 2017 at 01:35:33PM +0300, Maksim Salau wrote:
>> > +			} else if (object_is_on_stack(urb->transfer_buffer)) {
>> > +				WARN_ONCE(1, "transfer buffer is on stack\n");
>> > +				ret = -EAGAIN;
>> >  			} else {
>> 
>> Hi,
>> 
>> Has anyone considered a fail-safe mode? I.e.: if a buffer is on stack,
>> kmemdup it and continue with a warning. This will give us both: functional
>> drivers (with possibly decreased efficiency in speed and memory footprint)
>> and warnings for developers that a particular driver requires attention.
>
> No, I do not want that, let's fix the drivers.
>
>> This mode will not affect drivers which obey the rules, but will make
>> offenders at least functional. My main concern is that not every user is able
>> to detect and report a problem, which prevents drivers from functioning.
>> Especially this is a problem for not wide spread devices.
>> Due to this users a seeing unusable equipment, but developers are not
>> aware of those, even if fixes are trivial.
>> 
>> Such mode has a also a negative effect: if a developer has a device
>> with an offending driver, he can miss the warning message, since the driver
>> just works.
>
> Exactly, let's fix the bugs.  These have been bugs for 10+ years now,
> they should get fixed, it's not complex :)

We should probably have a similar patch on
drivers/usb/gadget/udc/core.c::usb_gadget_map_request_by_dev()

-- 
balbi